summaryrefslogtreecommitdiff
path: root/fs/btrfs/tests/btrfs-tests.c
diff options
context:
space:
mode:
authorFilipe Manana <fdmanana@suse.com>2023-11-21 16:38:38 +0300
committerDavid Sterba <dsterba@suse.com>2023-12-15 22:27:02 +0300
commit7dc66abb5a47778d7db327783a0ba172b8cff0b5 (patch)
tree66fef581a2f31904aae1c15f9fdbbc7aec798132 /fs/btrfs/tests/btrfs-tests.c
parentebb0beca6c6a2d33f809a74bad63261651237833 (diff)
downloadlinux-7dc66abb5a47778d7db327783a0ba172b8cff0b5.tar.xz
btrfs: use a dedicated data structure for chunk maps
Currently we abuse the extent_map structure for two purposes: 1) To actually represent extents for inodes; 2) To represent chunk mappings. This is odd and has several disadvantages: 1) To create a chunk map, we need to do two memory allocations: one for an extent_map structure and another one for a map_lookup structure, so more potential for an allocation failure and more complicated code to manage and link two structures; 2) For a chunk map we actually only use 3 fields (24 bytes) of the respective extent map structure: the 'start' field to have the logical start address of the chunk, the 'len' field to have the chunk's size, and the 'orig_block_len' field to contain the chunk's stripe size. Besides wasting a memory, it's also odd and not intuitive at all to have the stripe size in a field named 'orig_block_len'. We are also using 'block_len' of the extent_map structure to contain the chunk size, so we have 2 fields for the same value, 'len' and 'block_len', which is pointless; 3) When an extent map is associated to a chunk mapping, we set the bit EXTENT_FLAG_FS_MAPPING on its flags and then make its member named 'map_lookup' point to the associated map_lookup structure. This means that for an extent map associated to an inode extent, we are not using this 'map_lookup' pointer, so wasting 8 bytes (on a 64 bits platform); 4) Extent maps associated to a chunk mapping are never merged or split so it's pointless to use the existing extent map infrastructure. So add a dedicated data structure named 'btrfs_chunk_map' to represent chunk mappings, this is basically the existing map_lookup structure with some extra fields: 1) 'start' to contain the chunk logical address; 2) 'chunk_len' to contain the chunk's length; 3) 'stripe_size' for the stripe size; 4) 'rb_node' for insertion into a rb tree; 5) 'refs' for reference counting. This way we do a single memory allocation for chunk mappings and we don't waste memory for them with unused/unnecessary fields from an extent_map. We also save 8 bytes from the extent_map structure by removing the 'map_lookup' pointer, so the size of struct extent_map is reduced from 144 bytes down to 136 bytes, and we can now have 30 extents map per 4K page instead of 28. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/tests/btrfs-tests.c')
-rw-r--r--fs/btrfs/tests/btrfs-tests.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index ca09cf9afce8..b50cfac7ad4e 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -28,6 +28,7 @@ const char *test_error[] = {
[TEST_ALLOC_INODE] = "cannot allocate inode",
[TEST_ALLOC_BLOCK_GROUP] = "cannot allocate block group",
[TEST_ALLOC_EXTENT_MAP] = "cannot allocate extent map",
+ [TEST_ALLOC_CHUNK_MAP] = "cannot allocate chunk map",
};
static const struct super_operations btrfs_test_super_ops = {
@@ -185,7 +186,7 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
}
spin_unlock(&fs_info->buffer_lock);
- btrfs_mapping_tree_free(&fs_info->mapping_tree);
+ btrfs_mapping_tree_free(fs_info);
list_for_each_entry_safe(dev, tmp, &fs_info->fs_devices->devices,
dev_list) {
btrfs_free_dummy_device(dev);